Surface decontamination of frankfurters and other cooked sausage and processed meat and poultry products

ABSTRACT

Food products, such as precooked meats, raw meats, and poultry are treated with a decontaminant solution to remove surface microorganism contamination. The decontaminant solution contains peracetic acid at a concentration of from about 100 to 4000 ppm and has broad spectrum activity against a variety of pathogenic and spoilage microorganisms, such as  Listeria monocytogenes.

[0001] This application claims the priority of U.S. ProvisionalApplication Serial No. 60/143,892, filed Jul. 14, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to the food processing arts. Itfinds particular application in conjunction with thepost-pasteurization, surface microbial decontamination of hot dogs,sausages, and other processed meat and poultry products prior topackaging, and will be described with particular reference thereto. Itshould be appreciated, however, that the invention is also applicable tothe treatment of raw meat and poultry and other food products subject tomicrobial contamination.

[0003] Prevention of food poisoning is of paramount importance in thefood processing industry. Concern for food safety has lead mostcountries to regulate the food industry heavily to minimize publichealth risks. Despite these efforts, food poisoning still occurs. Manyinstances of food poisoning are attributed to bacteria, such asSalmonella, Clostridium, and Staphylococcus, among others.

[0004] Of rising concern is the relatively recent increase in theListeria contamination of poultry and processed food products, such asfrankfurters, other sausages, cheese, dairy food, and seafood. Processedmeat and poultry products such as frankfurters are generally cooked todestroy harmful bacteria. Of particular concern is the discovery thatpasteurized and fully cooked processed foods are being contaminated withmicrobes, such as Listeria monocytogenes, following cooking orpasteurization and prior to packaging for point of sale. Suchcontamination is typically surface contamination and is believed to becaused by the contact of microbes with food surfaces subsequent to heattreatment. Microbes such as Listeria may be airborne (i.e, carried bydust) or present on food contacting surfaces, such as processingequipment.

[0005] Recently, several outbreaks of food poisoning have been reportedin which the causative agent was suspected to be or identified asListeria contaminated food. Listeriosis is a serious disease which maycause meningitis, spontaneous abortion, and perinatal septicaemia.Although treatable with early diagnosis, untreated Listeriosis exhibitsa high mortality rate. In 1998, 20 deaths were associated with aListeria epidemic. Regulations now specify that food should beabsolutely free of Listeria, any contamination is considered to be anadulteration and the food should not be placed in commerce.

[0006] Food preservation by inhibition of growth of Listeriamonocytogenes is difficult. Listeria is a particularly difficultmicroorganism to destroy because it is heat resistant and is able togrow even under refrigeration in raw and cooked products. Methods fordestroying the organism on raw and on processed foods have includedtreatments using heat, radiation, chemicals, or antibiotics.

[0007] In the heat and irradiation treatments, the food products aresubjected to the heat or radiation after packaging. However, the heatresistance of the organism makes it difficult to achieve complete killthrough heat.

[0008] Antibiotics, such as Streptococcus lactis-derived or syntheticequivalent bacteriocin, such as nisin, have been used, either as aspray, or dip, or as a film on the packaging or casing which remains incontact with the food during heat treatment.

[0009] Chemicals used in treating the food products include ammoniumcompounds and acids such as citric, lactic and acetic acid, which havebeen used to wash down meat carcasses. With the chemical treatmentmethods, the carcass is placed on a conveyer system and thedecontaminating chemical is sprayed over the items as they pass beneath.Liquid smoke has been used on pasteurized processed foods to inhibitrecontamination after cooking. However, this imparts an undesirable,phenolic taste when used post-pasteurization.

[0010] If chemicals are to be used post-pasteurization, it is desirablethat they are both effective antimicrobial agents and non-hazardous toconsumers if they remain on the food product. Acids such as citric,lactic and acetic acids, while being safe for consumers, are not alwayscompletely effective at inactivating the microorganism. Even if one ortwo microorganisms remain on the food product, these can grow andmultiply under refrigeration to a level to which they are toxic to theconsumer by the time the product is sold.

[0011] The present invention provides for a new and improved apparatusand method for treating food products which overcomes theabove-referenced problems and others.

SUMMARY OF THE INVENTION

[0012] In accordance with one aspect of the present invention, a methodof treating a food product is provided. The method includes contactingan exterior of the food product with a decontaminant solution containingan antimicrobial agent, which includes peracetic acid, for a sufficienttime to microbially decontaminate the exterior of the food product.

[0013] In accordance with another aspect of the present invention, amethod of treating a food product is provided. The method includesspraying the food product with a solution comprising peracetic acid in afirst chamber and drying the food product in a second chamber.

[0014] In accordance with another aspect of the present invention, anapparatus for treatment of a food product is provided. The apparatusincludes first and second chambers. Spray nozzles are disposed in thefirst chamber for spraying a decontaminant solution over the foodproduct. The decontaminant solution includes peracetic acid. A pump isfluidly connected with a source of the decontaminant solution and thenozzles for supplying pressurized decontaminant solution to the nozzles.A source of a drying gas is connected with the second chamber for dryingthe decontaminated food product. A conveyor system conveys the foodproduct through the first and second chambers.

[0015] One advantage of the present invention is that pathogenicbacteria, such as Listeria, E. coli, and Salmonella are destroyed in ashort period of time.

[0016] Another advantage of the present invention is that the peraceticacid used to decontaminate the food products naturally degrades tonon-harmful reaction products, such as acetic acid and water, over ashort period of time.

[0017] Still further advantages of the present invention will becomeapparent to those of ordinary skill in the art upon reading andunderstanding the following detailed description of the preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating a preferredembodiment and are not to be construed as limiting the invention.

[0019]FIG. 1 is a schematic top view of a food treatment systemaccording to the present invention;

[0020]FIG. 2 is a schematic side sectional view of the food treatmentsystem of FIG. 1;

[0021]FIG. 3 is a schematic front view of the food treatment system ofFIG. 1; and

[0022]FIG. 4 is a perspective view of a system for treatment ofcarcasses.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A decontaminant solution containing peracetic acid has broadspectrum antimicrobial activity for treatment of exposed surfaces ofprocessed foods and raw meats and poultry. While particular reference ismade to the reduction in the species Listeria monocytogenes on cookedsausages, such as frankfurters, it should be appreciated that thedecontaminant solution is also effective for the reduction in otherpathogenic and spoilage microorganisms, such as Aeromonas hydrophila,Aerobacter butzleri, Bacillus cereus, Campylobacter jejuni, Eschericiacoli, Salmonella typhimurium, Staphylococcus aureus, and others on avariety of processed foods and raw meats and poultry. The term“decontaminate” and similar terms are used herein to encompass all formsof surface microbial decontamination, including disinfection andsterilization.

[0024] With reference to FIGS. 1-3, a system for treatment of foodproducts to remove surface contamination of microorganisms, such asListeria, includes a conveyor system 10, such as a moving conveyor belt.Food products to be treated 12, such as precooked meats, sausages, orother processed foods, raw meat, poultry, fish, whole carcasses, ordairy products are loaded onto the conveyor belt at position A. In thecase of sausages, such as frankfurters, these are preferably removedfrom their casing by peeling or other method prior to loading onto theconveyor system. The peeled frankfurters pass from the peeler to anorienting machine (not shown) which loads them on to the conveyor suchthat they are oriented perpendicularly to the direction of travel. WhileFIGS. 1-3 show the food products hanging from the conveyor on hooks 14,it is also contemplated that the food products be laid on a perforatedconveyor belt 10 and rotated during conveyance.

[0025] The conveyor system 10 carries the food products into a firstchamber or enclosure 20, where the food products are sprayed with thedecontaminant solution. Preferably, the conveyor system then carries thesprayed food products into a second chamber or enclosure 24 where arinse fluid is sprayed over the food products. Finally, the foodproducts are carried by the conveyor into a third chamber or enclosure26 where sterile air is blown over the products to dry them. The foodproducts are aseptically removed from the conveyor at point B andpackaged in sterile packaging for shipment.

[0026] Multiple spray nozzles 30 in the first chamber 20 spray thedecontaminant solution over the food products. The spray nozzles arepreferably arranged so that all surfaces of the food products arecontacted with the decontaminant solution. The spray nozzles may bearranged at the sides, above, and or below the processed food passingby. Alternatively, or additionally, the conveyor system 10 rotates thefood products as they pass by the nozzles 30 so that all surfaces arecontacted.

[0027] A pump 40 pumps the decontaminant solution from a reservoir 42 tothe spray nozzles through a supply line 44. Sprayed decontaminantsolution drips through openings 48 in the conveyor system and collectsin a sump 50 at the base of the chamber 20. Preferably, the pumpwithdraws the collected decontaminant solution from the sump through areturn line 52 and recycles it through the spray nozzles 30.

[0028] Periodically, the decontaminant solution is replaced orreplenished with fresh decontaminant solution from the reservoir 42 andthe used decontaminant is carried to a drain or otherwise disposed.Additionally, or alternatively, a sensor 54 detects the peracetic acidconcentration of the circulating decontaminant solution. A controller 56receives signals from the sensor. When the peracetic acid concentrationdrops below a predetermined level, the controller causes additionalperacetic acid to be supplied from the reservoir 42 to raise theperacetic acid concentration in the decontaminant solution flowing tothe nozzles.

[0029] The second chamber 24 is similar to the first chamber except inthat a rinse fluid is sprayed over the food products in place of thedecontaminant solution to remove substantially all of the peracetic acidfrom the food products. Specifically, a second pump 60 pumps the rinsefluid through a supply line 62 to nozzles 64 in the second chamber. Thesprayed rinse fluid passes through apertures 66 in the conveyor systemand collects in a sump 68 at the bottom of the second chamber. Thesprayed rinse fluid is returned to the pump by a return line 70.Alternatively, the return line directs the sprayed rinse fluid directlyto a drain 72.

[0030] Preferably, the rinse fluid comprises sterile water which is freeof all harmful microorganisms. A source of sterile water 74, such as asterile water generator, preferably receives tap water and destroysharmful bacteria in the water. The sterile water is then pumped from thesource 74 to the supply line 62 by the pump 60.

[0031] In the third chamber 26, an air manifold 80 blows sterile airover the food products to dry them. The air is generated by an air dryer82 which passes the dry air to the manifold via a forced air inlet line84. Air is returned from the chamber to the air dryer though an airreturn line 86 where it is dried and sterilized, such as by heating, andthen cooled to an appropriate temperature prior to returning the air tothe manifold 82.

[0032] The three chambers are aseptically connected with each other byconduits 90, 92 such that microorganisms are inhibited fromrecontaminating the food between the three stages. While 3 separatechambers are shown, it is also contemplated that the decontaminating andrinsing steps may be carried out in a single chamber, with the rinsenozzles 64 spaced a suitable distance from the decontaminant spraynozzles 30 so that there is little or no interference between therespective spray jets. While the air drying step may also be performedin the same chamber as the decontaminant and rinsing steps, it ispreferable to perform this step in a separate chamber, where humiditycan be reduced.

[0033] Optionally, the rinse step and rinse chamber are eliminated. Theperacetic acid in the decontaminant solution rapidly degrades over aperiod of a few hours to non-harmful products, such as acetic acid andwater, and thus traces of the decontaminant solution on the foodproducts are not harmful to consumers. Acetic acid (vinegar) is a commonadditive in many food products and is not harmful. Leaving a portion ofthe decontaminant solution on the food products ensures that they remainmicrobially decontaminated until packaging. The decontaminant solutionalso helps to keep the interior of the package sterile during packaging.Any remaining peracetic acid in the package degrades to harmlessproducts by the time packaged food products reach the store shelves orthe ultimate consumer.

[0034] It should be appreciated that the decontaminant solution is alsosuited to other methods of treatment of food products, such as dippingor immersing in the solution.

[0035] The decontaminant solution preferably contains from about 500 toabout 4,000 ppm of peracetic acid. The optimal concentration depends onthe length of time to which the food products are exposed to thedecontaminant solution and on the temperature of the decontaminantsolution. For example, a six log reduction (a reduction in the number ofmicroorganism of a factor of 10⁶) can be achieved by contacting thesurfaces of the food product with a 1,000 ppm peracetic acid solutionfor 12 seconds at 8° C. For ensuring complete elimination of resistantmicroorganisms, such as Listeria, longer times and/or higher peraceticacid concentrations are preferred. Preferred peracetic acidconcentrations are from about 1000 to about 2,000 ppm for contact timesof 30 seconds to 1 minute to ensure complete kill of Listeria and otherundesirable microorganisms at temperatures of from about 8-20° C.Microbiological analysis procedures are carried out periodically onsamples of the treated frankfurters to ensure that the conditions usedare maintaining a 100% kill of Listeria or other selectedmicroorganisms.

[0036] Tests with a variety of microorganisms have shown that theperacetic acid decontaminant solution has broad spectrum activityagainst a wide variety of pathogenic and spoilage microorganisms.Minimum inhibitory concentrations can be readily established for anyspecific microorganism or microorganisms to be destroyed.

[0037] The decontaminant solution may also contain other components,such as buffers, surfactants, chelating or sequestering agents, and thelike, provided that these are non-toxic (i.e., specified as “foodgrade”) or are rinsed thoroughly from the food products prior topackaging.

[0038] The peracetic acid for the decontaminant solution may be dilutedfrom a concentrate, such as a 30-38% peracetic acid in waterconcentrate. In one preferred embodiment, the concentrated peraceticacid is metered into the reservoir using a metering device, such as ametering pump 100. Or, the concentrated peracetic acid is provided as ameasured dose. For example, a measured dose of the liquid concentrate iscontained in a cup. The cup is opened, when needed, to release thecontents into a dilution liquid, such as water. Optionally, the cupcontains two or more compartments, with the liquid concentrate containedin one compartment and one or more of the other components of thedecontaminant solution, such as buffers, surfactants, corrosioninhibitors, etc., contained in a separate compartment or compartments.The compartments are opened when the decontaminant solution is to beused, either by the user, or by an automated opening device.

[0039] In an alternate embodiment, the decontaminant solution may beformed by reaction of two or more reagents which form the peracetic acidin water. For example, an acetyl donor, such as acetyl salicylic acid,and a persalt such as a perborate are mixed in water, where they reactto form the peracetic acid. In one embodiment, acetyl salicylic acid andsodium metaborate are separately contained in a two compartment cup,optionally together with other dry components of the decontaminantsolution. The cup is opened and the contents of the two compartments aremixed with a known quantity of water in the reservoir 42 to form thedecontaminant solution.

[0040] In yet another alternate embodiment, peracetic acid is generatedelectrolytically and supplied to reservoir 42.

[0041] The water for the decontaminant solution may be tap water ortreated water, such as distilled, filtered or sterile water. Optionally,all or part of the water may be replaced by other solvents.

[0042] The terms “chelating agents” and “sequestering agents” are usedsynonymously herein to encompass inorganic and organic compounds capableof forming coordinating complexes with metals. Suitable chelating agentsinclude, but are not limited to, ethylene diaminetetraacetic acid andits salts, cyclodextrins, hydrocarboxylic acids, such as citric acid;acetic acid, lactic acid, tartaric acid, and their salts, alone or incombination.

[0043] The decontaminant solution may also contain other antimicrobialdecontaminants, such as hydrogen peroxide, citric acid, lactic acid, oracetic acid, alone, or in combination.

[0044] A preferred pH for microbial decontamination by the peraceticacid is around neutral. Accordingly, the pH of the decontaminantsolution is preferably adjusted or buffered to a pH of between about 6.5and about 7.5. Phosphate buffer systems, which are acceptable in foodprocessing, are suitable buffers.

[0045] With reference to FIG. 4, an alternative embodiment of theapparatus of FIGS. 1-3 suitable to the treatment of meat carcasses isshown. A conveyor system 120 has a series of hooks 122 on which thecarcasses are hung. The conveyor system carries the carcasses through aspray 124 system similar to a car wash in which the decontaminantsolution is sprayed over the carcasses. As shown in FIG. 4, an invertedU-shape supply line 126 carries the decontaminant solution from areservoir 128 to a variety of spaced nozzles 130, via a pump 132. Thenozzles spray the decontaminant fluid over the carcasses. Sprayeddecontaminant solution drips from the carcasses and is collected inchannels 134 and returned to the reservoir supply or passed to a drain.Optionally, similar spray nozzles 140 spray a rinse fluid, such assterile water, over the carcasses.

[0046] For treating whole animals, the anti-microbial solution(described above) may be applied to the food animal after stunning, butbefore the animal is bled. In cases where a de-hairing or ade-feathering technology is applied, the application of peracetic acid,preferably occurs after the stunning and after the de-hairing orde-feathering processes, but before the animal is bled. Multiple spraynozzles are used in a specialized chamber designed to accommodate thespecies of food animal which will be treated. The chamber is designed toapply the anti-microbial solution to the entire surface of the animaland may be unique to each species of food animal (i.e., bovine, porcine,ovine, avian).

[0047] For animal carcass decontamination, the anti-microbial solutionis applied to the food animal carcass after stunning, de-feathering orde-hairing, and when applicable, after the removal of the hide or skin.The application utilizes multiple spray nozzles and, as for whole animaltreatment, occurs in a specialized chamber designed to accommodate thespecies of food animal carcass. Preferably, the carcass is treated atmultiple stages of the slaughter process, including pre-evisceration,immediately post-evisceration, and before and after the application ofother anti-microbial technologies. These may include hot water washes,organic acid rinses (lactic acid, acetic acid or citric acid), steamvacuuming, and steam pasteurization.

[0048] The treatment may also be applied to decontaminate heads, organs,offal and other carcass parts. The concentration of the anti-microbialsolution, contact time, temperature and other application parameters arecontrolled to optimize the effectiveness of the treatment.

[0049] In an alternative embodiment, the food products or carcasses aredipped into the decontaminant solution in place of being sprayed. Thedecontaminant solution may be contained in a bath and the food productimmersed in the solution for a period of from about five seconds up toabout one minute, or more, depending on the concentration of theperacetic acid used. The decontaminated food products may then berinsed, either by spraying a rinse solution over the food products or byimmersing the food products in a rinse solution, such as sterile water.

[0050] While not intending to limit the scope of the invention, thefollowing examples show the effectiveness of peracetic acid-baseddecontaminant solution in the destruction of bacteria, such Listeria,and other microorganisms.

EXAMPLES Example 1

[0051] Peracetic Acid Treatment of Pre-Cooked Frankfurters InoculatedWith Listeria monocytpgenes

[0052] Bacterial Cultures and Preparation of Inoculum

[0053] A five-strain mixture of Listeria monocytogenes was used forpurposes of inoculation. To prepare this mixture, five strains of L.monocytogenes were grown individually in tryptic soy broth (TSB) for48±2 h at 30° C. Equivalent aliquots of broth from each strain were thencombined in a sterile test tube to achieve a mixed inoculum containingapproximately equal populations of each of the five strains. The mixedculture was diluted as appropriate using 0.1% peptone diluent to achievea final mixed inoculum with a cell density of approximately 10,000colony forming units (cfu)/ml.

[0054] Inoculation of Frankfurter Samples

[0055] Packages of commercially prepared beef frankfurter sausages(“franks”) were obtained from a local retail outlet. TABLE 1 lists theconstituents of the franks, as provided on the packages. The packageswere stored at 4° C. until use (no more than 24 hours). Immediatelyprior to testing, the franks were removed from the commercial packagingand placed on a sterile surface in a biological safety cabinet. Thefranks were oriented on the surface such that no franks were in contactwith each other. Using a micropipette, each individual frank (except forthose used as controls) was inoculated with 0.1 ml of the previouslyprepared mixed inoculum with a target inoculation level of 1,000cfu/frank. A sterile bent rod was used to spread the inoculum over thefrank surface as evenly as possible. Inoculated franks were allowed toremain undisturbed on the sterile surface for at least 5 minutes priorto treatment with the decontaminant solution. Three franks wereinoculated per treatment to be evaluated, one frank being tested withoutinoculation. TABLE 1 Composition of Frankfurters Oscar Meyer Beef FranksIngredients: Beef, water, salt, <2% corn syrup, dextrose, flavor beefstock, sodium phosphates, autolyzed yeast, sodium erythorbate (made fromsugar), sodium nitrite, extractives of paprika Nutrition Facts: per 45 glink Calories 140 Cal. Fat 120 Total Fat 13 g (Sat. 6 g) Cholesterol 30mg Sodium 460 mg Total Carbohydrate 1 g Protein 5 g

[0056] Treatment of Frankfurter with Peracetic Acid

[0057] The peracetic acid used in the evaluation was obtained as a 35%concentrate under the trade name STERIS 20™ Sterilant Concentrate fromSTERIS Corporation (Mentor, Ohio). The concentrate was used without thebuffers or other additives supplied by the manufacturer. The concentratewas diluted to appropriate nominal concentrations (100, 500, and 1000ppm). Approximately 1 L of each concentration to be evaluated wasprepared in sanitized 2 L plastic containers. Additionally, 1 L of acontrol treatment, namely sterile distilled water (0 ppm peraceticacid), was also prepared in a 2 L container. Each of these fourconcentrations was evaluated using two exposure times, 2 and 10 seconds.Therefore, a total of eight treatments (four peracetic acidconcentrations (0, 100, 500, and 1000 ppm) at two exposure times (2 and10 seconds) were evaluated in this study. Each test was carried out twoor more times for establishing reproducibility.

[0058] Prior to treatment, one of the three inoculated franks pertreatment was evaluated for initial levels of L. monocytogenes (targetinitial population of 1,000 cells per frank). These franks were analyzedusing the quantitative procedures outlined below.

[0059] All peracetic acid treatments were performed inside a biologicalsafety cabinet. Inoculated franks were dipped into the peracetic acidtreatment solution (or distilled water for the 0 ppm samples) andallowed to remain submerged for either 2 or 10 seconds. Sterile utensilswere employed to remove the franks from the treatment solution andtransfer them to a sterile distilled water rinse. Franks were thensubmerged in a sterile water rinse and remained submerged for 2 or 10seconds (i.e., the same time as they were exposed to the peracetic acidsolution) and were removed with sterile utensils. Immediately afterremoval from the sterile water rinse, the franks were placed on asterile surface and allowed to air dry for 5 minutes.

[0060] For each peracetic acid concentration, three franks wereevaluated. Separate containers of sterile water rinse were employed foreach peracetic acid concentration×exposure time evaluated. All threefranks to be treated in a given concentration were dipped into a commonperacetic acid solution and a common sterile water rinse.

[0061] Following air drying, one frank per treatment was placed in asterile Stomacher bag and analyzed quantitatively for residual L.monocytogenes populations. The remaining two franks were retained insterile Stomacher bags and used for qualitative analysis, if necessary(in the event no surviving cells were detected using quantitativeprocedures).

[0062] Microbiological Analyses

[0063] To determine the number of surviving L. monocytogenes cells(quantitative evaluation), one frank per treatment was analyzed. Theweight of the frank was determined and an appropriate volume of 0.1%peptone diluent added to achieve a 1:5 dilution. These samples werehomogenized for 2 minutes using a Stomacher Lab Blender. Serialdilutions were prepared in 0.1% peptone diluent and appropriatedilutions plated using spiral and/or spread plate techniques on MOXagar. Agar plates were incubated at 30° C. for a total of 48 hours, withexamination at 24 and 48 hours. Typical L. monocytogenes colonies werecounted.

[0064] Similar evaluation procedures were used for counting the coloniesfor those franks treated with distilled water rather than peraceticacid, for the untreated franks (no peracetic acid, water or rinsetreatment), and for the franks treated with water or peracetic acidwithout prior inoculation.

[0065] The plating techniques used were capable of detection down to 5cfu/ml (1 colony/0.2 ml) for the spiral plating method and 0.5 cfu/mlfor the spread plating method (1 colony/2 ml). In the event that nosurviving L. monocytogenes cells were observed using direct platingprocedures, two franks per treatment were evaluated using qualitative(enrichment) procedures. A 10 mL aliquot of the retained homogenate wasplaced added to 90 mL of UVM broth to achieve a 1:10 dilution. Thesesamples were shaken by hand for 1 minute and incubated at 30° C. for 24h. Following this primary enrichment, 0.1 mL was transferred to 10 mL ofFraser broth and incubated at 30° C. for 24 h. This secondary enrichmentwas then used to perform an ELISA screening procedure (TECRA Listeriaspecies assay). Results of this qualitative analysis were used toindicate whether the sample was “positive” or “negative” for thepresence of Listeria species.

[0066] Differences in the observed reductions achieved with the variousconcentrations of peracetic acid were compared among the concentrationsas well as compared to the reductions achieved with the sterile watercontrol (o ppm).

[0067] TABLE 2 lists the peracetic acid concentration, temperature, andpH of the solutions used. TABLE 2 Temperature and pH of peracetic acidtreatment solutions immediately prior to use. Target PAA ActualTemperature Concentration PAA Conc. Exposure of PAA pH at PAA (ppm)(ppm) Time (sec) Solution (° C.) Solution Replication 1 1,000 1,146 1012.7 3.32   500 572 10 12.7 3.48   100 114 10 11.6 3.86    0 0 10 14.05.57 1,000 1,146 2 11.8 3.29   500 572 2 12.6 3.48   100 114 2 12.0 3.86   0 0 2 13.8 6.08 Replication 2 1,000 1,146 10 12.1 3.27   500 572 1011.8 3.48   100 114 10 12.3 3.85    0 0 10 13.6 6.17 1,000 1,146 2 11.93.29   500 572 2 11.7 3.49   100 114 2 12.5 3.86    0 0 2 13.5 6.18Replication 3 1,000 1,146 10 12.8 3.29   500 572 10 11.8 3.49   100 11410 12.5 3.85    0 0 10 13.8 6.05 1,000 1,146 2 12.9 3.30   500 572 211.6 3.50   100 114 2 11.8 3.86    0 0 2 15.1 6.07

[0068] TABLE 3 shows the quantitative and qualitative microbiologicalresults of analysis of the Listeria-inoculated franks. The targetinoculation level before treatment was 1,000 CFU/frank. It can be seenthat a 2 second treatment is sufficient to remove most, but not allListeria from the franks. A 10 second treatment reduces the Listeriacount below the detection limit of the quantitative assessmentprocedures, although a few colonies were detected in the qualitativeprocedure. The results indicate that some samples had actual populationsbefore treatment of <900 CFU/frank. Because the plating scheme had adetection limit of 900 CFU/frank, the actual populations of the samplesbefore treatment could not be determined in instances where thepopulation was <900 CFU/frank. Additionally, the plating scheme used forsamples analyzed after treatment had a detection limit of 90 CFU/frank.Therefore, the true population of any samples with a population of <90CFU/frank could not be specifically determined. For any samples that hada population of <90 CFU/frank after treatment, the retained homogenatewas analyzed using qualitative (presence/absence) procedures. Positiveindicates that at least one colony grew during the test. Negativeindicated that no colonies grew.

[0069] At the 0 ppm PAA concentration, all samples after treatment had apopulation of at least 90 CFU/frank, regardless of exposure time (2 or10 seconds). At the 100 ppm PAA concentration, regardless of exposuretime, in two of the three replications samples had populations of atleast 90 CFU/frank.

[0070] For a 10 second exposure time, samples treated in the 500 ppm PAAsolution had L. monocytogenes populations less than the detection limitof the quantitative plating procedure, however in two of the threereplications samples were found to be positive by qualitative analysis.At the 2 second exposure time, samples treated in the 500 ppm PAAsolution had populations of <90 CFU/frank in two of the threereplications, however these samples were found to be positive byqualitative analysis.

[0071] The 1000 ppm PAA solution, regardless of exposure time, resultedin populations of <90 CFU/frank in all three replications. For bothexposure times, two of the three ii samples analyzed by qualitativeanalysis were found to be positive for the presence of Listeria. TABLE 3Quantitative and qualitative microbiological data obtained from analysisof Listeria monocytogenes- inoculated frankfurters before and aftertreatment with solutions of peracetic acid with exposure times of 10seconds or 2 seconds. After PAA Concentration Treatment Estimated ActualBefore Treatment (CFU/ POS/ Conc.-ppm Conc.-ppm (CFU/frank) frank) NEG10 sec PAA exposure followed by 10 sec deionized water rinse  0 0 Rep 1900 90 — Rep 2 2,700   180  — Rep 3 <900* 90 — 100 114 Rep 1 <900* <90*POS Rep 2 1,800   180  — Rep 3 <900* 180  — 500 572 Rep 1 900 <90* POSRep 2 2,700   <90* POS Rep 3 1,800   <90* NEG 1000  1146 Rep 1 <900*<90* NEG Rep 2 900 <90* POS Rep 3 900 <90* POS 2 sec PAA exposurefollowed by 2 sec deionized water rinse  0 0 Rep 1 <900* 180  — Rep 2<900* 180  — Rep 3 <900* 90 — 100 114 Rep 1 <900* 180  — Rep 2 900 <90*POS Rep 3 1,800   90 — 500 572 Rep 1 900 <90* POS Rep 2 <900* <90* POSRep 3 <900* 90 — 1000  1146 Rep 1 900 <90* NEG Rep 2 1,800   <90* POSRep 3 <900* <90* POS

[0072] The results show that it is possible to remove substantially allListeria from a frankfurter in ten seconds dip treatment. It should beappreciated that the frankfurters tested were inoculated with massiveamounts of Listeria, relative to what would be expected in practice,demonstrating the ability of peracetic acid to decrease Listeriacontamination by orders of magnitude.

[0073] Further tests using 2000 ppm sprayed over the frankfurters for 30seconds to one minute showed even higher kill levels, with complete killbeing achieved.

EXAMPLE 2

[0074] D-Values for Listeria monocytogenes in Peracetic Acid Solutions

[0075] Peracetic acid solutions of 500, 1000, and 2000 mg/L (ppm) wereprepared as for Example 1, using deionized water. To 100 mL samples ofthe solutions, 1.7×10⁶ Listeria monocytogenes ATCC. 43256 per mL wereadded and mixed. The samples were maintained at a preselectedtemperature (° C.° C., ˜15° C., or ˜22° C.). At 10, 20, 30, 40, and 50seconds contact time, 1 mL was removed, neutralized, and the Listeriamonocytogenes organisms remaining were determined by plating on TSA andincubation. Results showed that the microorganism was destroyed in allcases, except for the sample exposed to 500 mg/L at ˜8° C. for only 10seconds. D-values (time required to kill one log of the testmicroorganism—in this case, a reduction in microorganisms from 1.7×10⁶initially to 1.7×10⁵) were determined, as shown in TABLE 4. D-valuesbelow the detection limit of the test are shown as <2 seconds. TABLE 4D-values for Listeria monocytogenes Peracetic acid concentrationTemperature D-value (mg/L) Range (° C.) pH range (seconds) 500 8.3-8.53.7-3.7 2 500 14.7-15.0 3.4-3.6 <2 500 22.7-22.8 3.4-3.6 <2 1000 8.1-8.13.2-3.4 <2 1000 15.0-15.2 3.2-3.4 <2 2000 8.1-8.4 3.0-3.1 <2 20003.0-3.1 3.0-3.1 <2

EXAMPLE 3

[0076] Stability of Peracetic Acid Solutions

[0077] Peracetic acid solutions were prepared in deionized water as forExample 2 to nominal concentrations of 1000 and 2000 mg/L. Actualperacetic acid concentrations were measured at 0 and 30 minutes ataround 25° C. and 50° C. Results shown in TABLE 5 indicate that thesolutions remained relatively stable over the 30 minute period. TABLE 5Stability of peracetic acid solutions at 25 and 50° C. over 30 minutesConcentration Concentration Temperature at 0 mins at 30 mins (° C.) pH(mg/L) (mg/L) 26-29 2.7 1347 1355 50 2.7 1310 1284 26-29 2.6 2016 201750 2.6 1937 1959

EXAMPLE 4

[0078] Minimum Inhibitory Concentration of Acetic Acid, Lactic Acid,Peracetic Acid, and Liquid Smoke on Generic Escherichia coli andSalmonella spp.

[0079] The minimum inhibitory concentration (MIC) was determined forfive strains of E. coli and five strains of Salmonella spp. as listed inTABLE 6, using acetic acid, lactic acid, peracetic acid, and liquidsmoke. TABLE 6 Strains of E. coli and Salmonella used in MIC StudiesMicroorganism Strain E. coli ATCC. 4350 E. coli ATCC 35336 E. coli ATCC9546 E. coli ATCC 12043 E. coli ATCC 25922 Salmonella enteritidisUSDA-FSIS 15060 Salmonella newport ATCC 6962 Salmonella typhimurium Dr.S. Bailey, USDA-ARS, Athens, GA Salmonellalille Dr. L. Beuchat,University of Georgia, Griffin, GA Salmonella montevideo Dr. L. Beuchat,University of Georgia, Griffin, GA

[0080] Each strain was subcultured on tryptic soy agar (TSA, DIFCO,Detroit, Mich.) slants and stored at 4° C. Strains were individuallytransferred into 100 mL of sterile 2×BHI (DIFCO, Detroit, Mich.) andincubated at 35° C. for 24 hr. to reach ca. 10⁹ colony forming units/mL(CFU/mL). Then, 25 mL of each strain of E. coli was transferred into asterile bottle (mixture X), and 25 mL of each strain of each strain ofSalmonella spp. was transferred into a sterile bottle (mixture Y).Mixtures X and Y were maintained separately throughout the test.

[0081] The average initial inoculum levels of E. coli and Salmonellaspp. were ca. 1.0×10⁹ CFU/mL, and ca. 8.4×10⁸ CFU/mL, respectively.

[0082] Serial dilutions were made using Butterfields' Phosphate Buffer(BPB, Sigma, St. Louis, Mo.) in 1 mL aliquots prior to inoculation. BPBwas prepared as a stock solution by adding 34 g of KH₂PO₄ to 500 mL ofdistilled water. The pH was adjusted to 7.2, and the solution wasbrought to a volume of 1 L. The BPB stock was autoclaved for 20 min. at121° C. and 15 lbs. of pressure. For each of the treatments to beevaluated, (acetic acid, lactic acid, peracetic acid, and liquid smoke)a 10 mL test tube containing 1 mL of buffer, 1 mL of treatment, and 1 mLof mixture X or Y was prepared. For glacial acetic acid (U.S.P.-F.C.C.,J.T. Baker, Phillipsburg, N.J.), starting concentrations and serialdilutions were 50%, 25%, 12.5%, 6.25%, 3.12%, 1.56%, 0.78%, 0.39%, and acontrol (no treatment, buffer and culture). For lactic acid, 86.30%(U.S.P.-F.C.C., J.T. Baker, Phillipsburg, N.J.), starting concentrationsand serial dilutions were 43.15%, 21.58%, 10.79%, 5.39%, 2.70%, 1.35%,0.67%, 0.33%, and a control. For peracetic acid 35.0% (STERIS 20™,STERIS Corporation, Mentor, Ohio), starting concentrations and serialdilutions were 17.5%, 8.75%, 4.38%, 2.19%, 1.09%, 0.55%, 0.30%, 0.14%,0.07%, 0.03%, and a control. For liquid smoke (Hickory Specialties,Brentwood, Tenn.) starting concentrations and serial dilutions were 50%,25%, 12.5%, 6.25%, 3.12%, 1.56%, 0.78%, 0.39%, and a control. Dilutionswere prepared with deionized water.

[0083] The test tubes were incubated at 35° C. for 24 hrs. and turbiditywas evaluated using McFarland equivalence standards, to study thebacteriostatic properties of the diluted solutions. In addition, eachdilution was plated to evaluate the bactericidal properties of thediluted solutions. Using a 1 μL sterile loop, each concentration andcontrol for either microorganism mixture was streaked on plate countagar (PCA, DIFCO, Detroit, Mich.). A selective agar was also used foreach mixture, eosine methylene blue agar (EMB, DIFCO, Detroit, Mich.)for E. coli and xylose lysine decarboxylase agar (XLD, DIFCO, Detroit,Mich.) for Salmonella spp. All plates were incubated for 24 hrs. at 35°C. and were inspected for growth or no growth.

[0084] All four treatments were effective in inhibiting the growth ofgeneric E. coli and Salmonella spp. at different levels in laboratorymedium. A summary of the treatments, microorganisms, and final minimuminhibitory concentration (MIC) can be found in TABLE 7. Peracetic acidinhibited the growth of E. coli and Salmonella spp. at the lowestconcentration (0.137%) of all three acids tested. TABLE 7 Minimuminhibitory concentrations of liquid smoke, acetic acid, lactic acid, andperacetic acid for E. coli and Salmonella spp. Treatment MIC (%)Peracetic Organism Liquid Smoke Acetic Acid Lactic acid acid E. coli6.25 3.12 2.70 0.14 Salmonella 6.25 0.78 1.35 0.14 spp.

EXAMPLE 5

[0085] Reduction of Generic Escherichia coli and Salmonella spp. on PorkSkin With Water, Acetic Acid, Lactic Acid, or Peracetic Acid.

[0086] Samples of pork skin were inoculated separately with either 5strains of E. coli or 5 strains of Salmonella spp. (mixtures X and Y,see Example 4). Five different treatments were evaluated foreffectiveness in reducing bacteria on pork skin. The treatments weredeionized water, 2% acetic acid, 2% lactic acid, 0.1% peracetic acid,and a control (no treatment), respectively. EMB agar was used for E.coli and XLD for Salmonella, and a nutrient agar was also used for E.coli and Salmonella for total count.

[0087] Bacterial Cultures

[0088] The five strains of generic E. coli and five strains ofSalmonella spp. were cultured and transferred individually into 100 mLof tryptic soy broth (TSB, DIFCO, Detroit, Mich.) with 1% dextrose(Sigma, St. Louis, Mo.) in duplicate. Dextrose was added to induce acidtolerance in the microbial cell. The cultures were incubated at 35° C.for 24 hrs. to obtain ca.10⁹ colony forming units (CFU)/mL. The cellswere harvested by the centrifuging each culture at 10,000×g force for 10min. at 4° C., (Beckman J2-HS centrifuge, Beckman Instruments, Inc.,Palo Alto, Calif.). After centrifugation, the supernatant was pouredoff, and cells remained in pellet form. Each pellet was individuallyre-suspended with 50 mL of 0.1% peptone water (DIFCO, Detroit, Mich.).All five strains of E. coli or Salmonella spp. inoculum were transferredto separate HDPE plastic spray bottles (Sprayco™, Detroit, Mich.) to beused in the mist inoculation of pork skin samples.

[0089] Media

[0090] For E. coli, PCA and EMB media were used, and for Salmonella, PCAand XLD media were used. Bacto Plate Count Agar (PCA) was used in thisstudy as a standard methods medium for the enumeration of bacteriabefore and after treatments. Spiral (sl) or spread (sd) plate techniquewere used for viable cell counts. Duplicate plates were performed foreach treatment.

[0091] Pork Sample Preparation

[0092] Fresh pork skins taken from the loin region were cut torectangles of 19.35 cm². A hole was bored into the top of each sample sothat each sample could be suspended from an individual hook in the spraycabinet. Samples were laid out onto trays wrapped in butcher paper. Eachtray was individually spray inoculated with E. coli or Salmonella spp.in a Plexiglas spray chamber to ca.8.4 mL of inoculum. After theinoculation, each tray was placed under a laminar flow hood for 1 hr. toallow the surface to dry and for the attachment of the bacteria to thepork skin.

[0093] The peracetic acid (PAA) used in this study was a 35.0% PAAbuffered, liquid solution prepared from a STERIS 20™ two compartment cup(a dry powder containing anticorrosive additives, buffers, sequestrants,and surfactants). The peracetic acid determined before each use of thetreatment using a calibration curve.

[0094] Treatment Application

[0095] Five inoculated samples were individually placed on stainlesssteel hooks in a spray cabinet at ambient temperature.

[0096] The samples were exposed to a continuous spray of the selectedtreatment for 5 seconds at a spray pressure of 16-18 psi.

[0097] The treated samples were placed into individual stomacher bagscontaining 30 mL of 0.16 peptone water (DIFCO, Detroit, Mich.) andstomached for 2 min. Serial dilutions of 0, 10⁻², and 10⁻⁴ were spiralplated (WASP spiral plater, Bioscience International, Rockville, Md.) onPCA (DIFCO, Detroit, Mich.) and EMB (DIFCO, Detroit, Mich.) for E. coliand on plate count agar (PCA, DIFCO, Detroit, Mich.) and xylose lysinedecarboxylase agar (XLD, DIFCO, Detroit, Mich.) for Salmonella spp.Samples were also spread plated on PCA and EMB agar for E. coli or PCAand XLD agar for Salmonella spp, using 0.25 μL/plate for a total of 1 mLon 4 plates. This was to ensure a countable plate. Plates were invertedand incubated at 35° C. for 24 hrs. (48 hrs. for Salmonella spp.).

[0098] Titratable Acidity And pH

[0099] Titratable acidity (TABLE 8) was determined according to AOACmethods (JAOAC 30, 130: 1947;34,239: 1951), sing a {fraction (1/10)}dilution factor. Phenylethylene was used as the indicator with 0.1N NaOHas the base. The pH of acetic and lactic acid was determined during eachreplication using a standardized pH meter (Orion Research, Inc.,Beverly, Mass.). TABLE 8 Average titratable acidity and pH values foracetic and lactic acid used on Escherichia coli and Salmonella spp.Treatment Microorganism Titratable Acidity (mL) pH Acetic acid E. coli2.65 2.54 Acetic acid Salmonella spp. 2.45 2.55 Lactic acid E. coli 2.072.10 Lactic acid Salmonella spp. 1.93 2.08

[0100] Microorganism Count

[0101] Microorganism counts on the different agar plates are provided inTABLE 9. TABLE 9 Log CFU/cm² of Eschericia Coli and Salmonella spp. oninoculated pork skins after 24 hours (E. coli)/ 48 hours (Salmonella)Total Count Total Count Total Count Total Count (E. coli) on (E. coli)on (Salmonella) (Salmonella) Treatment PCA EMB on PCA on XLD Notreatment 6.55 6.54 6.46 5.72 Water 5.25 5.15 6.05 5.78 2% Lactic acid3.96 4.02 4.95 2.97 0.1% Peracetic 3.28 3.04 5.34 3.83 Acid 2% Acetic4.68 4.55 5.37 4.27 Acid

[0102] Peracetic acid (0.1%) (PAA) can be seen to be an effectiverinsing agent for Salmonella and E. coli, even though used at much lowerconcentration than the lactic acid or acetic acid. Acetic acid, lacticacid, and peracetic acid were all found to be effective in inhibitingthe growth of E. coli and Salmonella spp. at lower concentrations thanfor liquid smoke. As seen from TABLE 7, the minimum inhibitoryconcentration (MIC) using the test tube dilution method indicated thatthe most effective antimicrobial for generic E. coli and Salmonella spp.was peracetic acid. Liquid smoke had the highest MIC of 6.25% for E.coli and Salmonella spp. compared to the organic acids.

[0103] Peracetic acid (0.1%) was the most effective treatment on porkskin for E. coli, achieving 3 log/cm² reduction and was significantly(p≦0.05) different from all other treatments. Lactic acid (2%) was themost effective treatment for Salmonella spp., achieving almost 3 log/cm²reduction. After 24 hrs. Salmonella spp. showed little to no recovery;therefore, an additional 24 hrs. incubation period was evaluated. Thissuggested that the Salmonella spp. were more susceptible to acid injurycompared to E. coli cells.

[0104] The selective agars used suggested higher reductions than thenutrient agar.

[0105] The studies suggest that decontamination rinses are effective inreducing the amount of bacteria in laboratory media and on pork skin.

[0106] Statistical Analysis

[0107] Bacterial enumeration data from the three replications of E. coliand Salmonella spp. were analyzed by the analysis of variance using theGeneral Linear Model procedure of Statistical Analysis System (SASInstitute, Inc., 1990). LSD was used to separate the means of the logCFU/cm² samples.

[0108] For generic E. coli, all treatments were significantly different(ps0.05) on both PCA and EMB. For Salmonella spp. on PCA, there were nosignificant differences (>0.05) between the samples that were treatedwith water (W) and the samples that were untreated (NT). Acetic acid(AC) showed no significant difference (p>0.05) from lactic acid (LA), orperacetic acid (PAA), indicating that the organic acids were reducingSalmonella spp. to approximately the same level. For Salmonella spp. onXLD, there were significant differences (p≦0.05) between the untreatedsamples (NT) and the samples treated with water (W). Acetic acid (AC)and peracetic acid (PAA) were not significantly different (p>0.05). Thelactic acid (LA) treatment was significantly different (p≦0.05) from allother treatments.

[0109] The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

Having thus described the preferred embodiment, the invention is nowclaimed to be:
 1. A method of treating a food product comprising:contacting an exterior of the food product with a decontaminant solutioncontaining an antimicrobial agent which includes peracetic acid for asufficient time to microbially decontaminate the exterior of the foodproduct.
 2. The method of claim 1, further including: rinsing themicrobially decontaminated food product to remove the decontaminantsolution.
 3. The method of claim 1, further including: sterile dryingthe decontaminated food products.
 4. The method of claim 1, wherein theperacetic acid in the decontaminant solution is at a concentration offrom about 100 to about 4000 ppm.
 5. The method of claim 1, wherein theperacetic acid concentration is from about 1000 to about 2000 ppm. 6.The method of claim 1, wherein the step of contacting the food productwith the decontaminant solution includes spraying the decontaminantsolution over the food product.
 7. The method of claim 6, wherein thefood product is sprayed with the decontaminant solution for a period offrom about 10 seconds to 5 minutes.
 8. The method of claim 7, whereinthe food product is sprayed with the decontaminant solution for a periodof from about 1 to 2 minutes.
 9. The method of claim 6, wherein the stepof contacting the food product with the decontaminant solution includestransporting the food product on a conveyor past spray nozzles whichspray the decontaminant solution over the food product.
 10. The methodof claim 6, further including: recirculating the sprayed decontaminantsolution.
 11. The method of claim 1, wherein the food product compriseshot dogs and the method further includes, prior to the step ofcontacting the exterior of the food product: removing the hot dogs fromcasing skins.
 12. The method of claim 3, further including, after thestep of drying the food product: aseptically packaging the food product.13. A method of treating a food product comprising: a) spraying the foodproduct with a solution comprising peracetic acid in a first chamber;and b) drying the food product in a second chamber.
 14. The method ofclaim 13, further including: c) after step a), rinsing the food productwith a rinse fluid in a third chamber intermediate the first and secondchambers.
 15. The method of claim 13, further including: conveying thefood product through the first and second chambers on a conveyor system.16. An apparatus for treatment of a food product comprising: a firstchamber; spray nozzles disposed in the first chamber for spraying adecontaminant solution over the food product, the decontaminant solutionincluding peracetic acid; a source of the decontaminant solution; a pumpfluidly connected with the source of the decontaminant solution and thenozzles for supplying pressurized decontaminant solution to the nozzles;a second chamber; a source of a drying gas connected with the secondchamber for drying the decontaminated food product; and a conveyorsystem which conveys the food product through the first and secondchambers.
 17. The apparatus of claim 16, further including: a thirdchamber intermediate the first and second chambers, the conveyor systemconveying the food product through the third chamber; a source of arinse fluid connected with the second chamber which delivers a rinsefluid to the second chamber for rinsing the decontaminated food product.18. The apparatus of claim 16, further including: a recirculation systemwhich recirculates the sprayed decontaminant solution to the nozzles.